1. Field of the Invention
The present invention relates to a beta zeolite catalyst for the preparation of a BTEX (benzene, toluene, ethylbenzene, xylene) mixture from polyaromatic hydrocarbons and a preparation method of the same.
2. Description of the Related Art
In coping with the continued high oil price and deepening environmental problems, it is important strategy to upgrade the lower value heavy oil fraction containing a high content of polyaromatic compounds to the higher value middle distillate including diesel and BTEX (benzene, toluene, ethylbenzene, xylene).
Hydrogenation process and hydrocracking process are the two most representative methods to treat the polyaromatic compounds included in heavy oil fractions. In such processes, if naphthalene, one of the most representative polyaromatic hydrocarbons, is taken as an example, it is converted into alkyl benzene like BTEX through a series of hydrogenolysis in the presence of a catalyst.
At this time, the usable catalyst is a zeolite catalyst containing metals. The said zeolite catalyst is a bifunctional catalyst, so that the combined characteristics of both the acid function obtained by the zeolite support and the metal function are shown.
Particularly, the characteristic of the acid catalyst included in a zeolite support is the ability to induce dehydrogenation, cracking, isomerization, and dealkylation, and the characteristic of the metal material is the ability to induce hydrogenation, hydrogenolysis, and isomerization.
The balance and harmony between the acid catalyst characteristic and the metal catalyst characteristic is important for the bifunctional catalyst to be fully functioning in order to prepare a middle distillate and BTEX from polyaromatic hydrocarbons. Therefore, it is essential to make optimization of choice of metal materials, supports, and metal load, etc.
As a support, silica-alumina, alumina, or various zeolites can be used. The zeolite herein can be selected from the group consisting of ZSM-5 zeolite having 10-ring structure, HY zeolite having 12-ring structure, and beta zeolite.
In particular, the said zeolite has the well-developed micropores and the catalyst based on such zeolite has been applied to various acid-catalyzed reactions due to the pore structure containing proper acid sites.
In the previous study about the catalytic conversion into BTEX, an aromatic compound being widely used as a basic material in the field of petrochemistry, alkylbenzenes were able to be produced with a high yield by hydrocracking 1-methylnaphthalene using NiMo/Al2O3/USY (Ultra Stable Y zeolite) as a catalyst. According to the previous reports, Ni2P/Beta catalyst was efficient in producing alkylbenzenes with a high yield via naphthalene hydrogenolysis among Ni2P catalysts supported on various supports (SiO2, ZSM-5, Beta, or USY) (see non-patent references 1 and 2).
The present inventors studied to prepare an efficient catalyst for the conversion of polyaromatic hydrocarbons into products containing BTEX, the basic oil resource in the field of petrochemistry, wherein the catalyst is precisely capable of upgrading the lower value heavy oil fraction containing a high content of polyaromatic compounds produced from petroleum. As a result, the present inventors confirmed that the beta zeolite catalyst of the invention displayed not only a high conversion of polyaromatic hydrocarbons but also a high BTEX production yield, and accordingly the inventors completed this invention by confirming that the beta zeolite catalyst of the present invention can be effectively used as a catalyst for the production of BTEX.